Polymers of carbon monoxide and ethylenically unsaturated hydrocarbons, commonly called polyketones, have been known and available for some time. High molecular weight linear alternating polyketones are of considerable interest because they exhibit good physical properties. These polymers can be represented by units of the repeating formula ##STR1## wherein A is the moiety obtained by the polymerization of an ethylenically unsaturated hydrocarbon through the ethylenic unsaturation. This class of polymers is disclosed in numerous U.S. patents assigned to Shell Oil Company and is exemplified by U.S. Pat. Nos. 4,880,865 and 4,818,811 which are incorporated herein by reference.
These polymers are relatively high molecular weight materials having established utility as premium thermoplastics in the production of shaped articles such as containers for food and drink and parts for the automotive industry. These articles and applications can be produced by processing the polyketone polymer according to well known methods.
Semi-crystalline polymers tend to have good chemical resistance but have dimensional stability and toughness characteristics that are not optimal for certain applications. Amorphous polymers, on the other hand, tend to have better dimensional stability than semi-crystalline polymers (less mold shrinkage, and lower coefficient of thermal expansion in useful temperature ranges) and in some instances exhibit better toughness. However, amorphous polymers invariably exhibit chemical resistance characteristics that are inferior to those of semi-crystalline polymers. Indeed, they can be completely insuffuicient for certain applications. Generally, polymer blends possess an average of the properties found in the components. U.S. Pat. No. 4,880,908 to Lutz and Gergen is drawn to a blend of polyketone (which is semi-crystalline) and polycarbonate (which is amorphous). Thus, one might consider a blend of the two types of polymers. Unfortunately, it is has been found that when such blends have been produced the overall properties have not been adequate for certain applications because the two types of polymers have limited compatibility.
In the case of polyketone polymers, it would be advantageous to retain the more desirable properties of the polyketone polymers and yet improve other properties. Finding the correct types and proportions of polymers that will comprise such a blend and determining whether such blends are workable can be complex.
Generally, polymer blends can be classified as either miscible (single-phase) or immiscible (multi-phase). Most combinations of polymers are immiscible. The formation of a dispersed phased in a continuous phase and phase separation (e.g., upon changing temperatures) are common occurrences. Blend morphology can thus be a dynamic phenomenon especially during processing. The introduction of compatibilizers is one method of stablizing and improving the internal structure, or morphology of the blend. Such substances can alter the interfacial tension of blend phases or work via mechanisms such as the formation of an interpenetrating polymer network (IPN) to improve adhesion between phases. Employing theoretical considerations to such problems is not an entirely reliable approach. For example, it has often been found that model compounds that may suggest one or the other such formulations are amenable to a particular mechanism proves to be inaccurate when the polymeric analogues of those models are employed.
Futhermore, the term "blend compatibility" is a utilitarian one. It is used as an overall description of the properties of the blend relative to the expected weighted average properties of the pure constituents. The properties in question are those most relevant to the application of the blend. As such, determining whether a given blend is compatible may be specific to the requirements of the planned application. Nevertheless, it is has been found that among multiphase blends, compatibility generally increases as the strength of the blend interface increases. Thus, most efforts directed toward improving the compatibility of a polymer blend are concerned with strengthening this interfacial region.
Compatibilized polyketone/polycarbonate blends which present properties that are better than those of the binary blends would enhance the range of applications of such blends.